Local hypothalamic blood flow during sleep.

There are several hypotheses to explain the observed rise in hypothalamic temperature during REM sleep. One of theories suggests that the increase in temperature is due to an increase in local blood flow. In order to test this hypothesis local hypothalamic blood flow (HBF) was measured during wakefulness, HBF increased by 63% and 25% during REM and non-REM sleep respectively. It is possible that the increase of HBF during REM sleep is due to the activation of the recently described noradrenergic pathways from the brain stem to the cortex.